Houses built in the 1920s share a common technical base: load-bearing walls made of brick or stone, wooden floors, and roofs made of slate or mechanical tiles. This construction vocabulary, inherited from the 19th century, is nonetheless transformed by the effect of two simultaneous forces. The massive reconstruction of regions devastated by the 1914-1918 war imposes unprecedented rhythms. The aesthetic currents of the interwar period, led by Art Deco, renew the facades and volumes.
Reinforced concrete in 1920s houses: a still hybrid material
Reinforced concrete existed before 1920, but its use was limited to civil engineering works and industrial buildings. In the decade following the war, it gradually entered individual housing. Foundations and lintels were the first elements to benefit from it, as they advantageously replaced cut stone, which had become expensive and difficult to source.
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The walls remain predominantly in traditional masonry: solid brick in the North and East, limestone rubble in the Paris Basin, and millstone grit in Île-de-France. Reinforced concrete serves as structural reinforcement (chains, corner posts) rather than as a facade material. This coexistence of old and modern techniques defines residential construction of the period.
To better understand how these processes combined daily on the construction sites of the time, the 1920s houses on Maison Art Déco detail the typical assemblies of this decade.
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The floors illustrate this transition well. In the most modest houses, wooden joists persist on all floors. In more carefully constructed buildings, a reinforced concrete slab appears on the ground floor, while the upper floors retain their joists. This mixed wood-concrete structure complicates current renovations, as each level follows a different load-bearing logic.
Art Deco and regionalism: two architectural currents in the same decade
The 1925 International Exhibition of Decorative Arts in Paris gives its name to the style that marks the period. Art Deco facades are recognized by their geometric lines, simplified cornices, and relief patterns (suns, chevrons, stylized flower baskets). The cladding materials also change: ceramic stoneware mosaics, colored faience cabochons, and ornamental wrought iron replace classical moldings.
However, the Art Deco style covers only a fraction of the residential buildings of the 1920s. In the Somme and Pas-de-Calais, Reconstruction produced thousands of houses that borrow from architectural regionalism: Flemish-inspired gables, decorative half-timbering reminiscent of Norman style, or two-tone brick facades forming simple geometric patterns. These houses combine a modern layout (separate kitchen, bathroom, distribution corridor) with cladding that evokes pre-war local traditions.
Facade decorations and ironwork
Artistic ironwork reached a peak of production in the 1920s. Railings, imposts, canopies: wrought or beaten iron complements the facade with floral or geometric motifs. These elements, often made by local artisans, now serve as reliable dating indicators to identify a house from this period.
- Railings with scroll or spiral motifs, fixed on molded concrete or reconstructed stone balconies
- Glazed imposts above entrance doors, sometimes adorned with colored geometric stained glass
- Iron and glass canopies protecting the threshold, with ornate consoles characteristic of the Art Deco vocabulary
Insulation and thermal performance: the structural weak point of 1920s buildings
The walls of 1920s houses contain no thermal insulation. Solid brick, 20 to 30 cm thick, offers reasonable inertia in summer, but its winter thermal performance is very low compared to current standards. The original windows, made of single-glazed wood, exacerbate heat loss.
The energy renovation of these houses poses a technical dilemma. External insulation masks the ornamented facades, effectively destroying the architectural identity of the building. Internal insulation reduces living space and can create condensation points in old walls if the vapor barrier is poorly installed.
Ventilation and humidity
These houses originally operated with natural ventilation due to a lack of airtightness: imperfect window seals, open chimneys, absence of a membrane under the roof. Any intervention that makes the envelope more airtight (changing windows, insulation, removing a chimney) must be accompanied by a mechanical ventilation system. Without this, humidity concentrates in the walls and causes accelerated degradation.
- Check compatibility between the existing interior plaster (often lime-based) and the proposed insulating materials
- Prefer breathable insulators (wood fiber, hemp wool) to maintain the wall’s ability to expel water vapor
- Install a suitable mechanical ventilation system as soon as the envelope’s airtightness is modified
20th-century heritage: a developing status for 1920s houses
For a long time, houses from the 1920s received no heritage recognition. Too recent for classification schemes inherited from the 19th century, too ordinary to attract the attention of architectural historians, they underwent decades of uncontrolled modifications: cement facades, replacement of wooden joinery with white PVC, removal of facade decorations.
The situation is evolving. The buildings of the 1920s are gradually entering the realm of protected heritage. Since 2024, the Walloon Heritage Agency has been disseminating educational materials on 20th-century architecture aimed at 8-12 year-olds, a sign that awareness is starting early. Furthermore, registration on the heritage inventory, when it exists, triggers a special regime of demolition control with mandatory public hearings.
This recognition remains partial and uneven across territories. A well-preserved Art Deco house in a reconstructed city in the North will more easily receive institutional attention than an isolated regionalist pavilion in a rural area. Protection still largely depends on local mobilization, leaving a significant portion of this heritage exposed to irreversible transformations.